title: Reduced fat oxidation rates during submaximal exercise in boys with cystic fibrosis.
abstract: BACKGROUND
  Exercise is a viable form of therapy for children with cystic fibrosis (CF). Understanding the energy sources used during exercise would aid CF patients in obtaining proper nutrition in order to sustain an active lifestyle.
  
  
  METHODS
  Six boys with CF (mean age ± SD: 14.8 ± 2.3 yrs, FEV1: 99 ± 18% predicted) and six matched controls (14.0 ± 2.2 yrs) completed a session of two 30 min bouts of cycling at an intensity set at 50% peak mechanical power. Rates of total fat and carbohydrate (CHO) oxidation were calculated from expired gases. Plasma insulin, glucose and free fatty acid (FFA) were determined before, during and at the end of the exercise.
  
  
  RESULTS
  Rates of fat oxidation (expressed in mean mg × kg body weight(-1) × min(-1) ± SD) were significantly lower in children with CF (5.7 ± 1.6) compared to controls (8.6 ± 1.8, p < 0.05). Children with CF also had lower values than controls in amount of fat oxidized (CF: 17.3 ± 5.0 g, controls: 26.1 ± 5.9 g, p < 0.05) and percent of total energy expenditure from fat (CF: 32 ± 6%, controls: 43 ± 7%, p < .0.05), but a higher contribution from CHO (CF: 68 ± 6%, controls: 57 ± 7% p < .0.05). Plasma FFA was significantly lower in children with CF compared to controls during (CF: 252.5 ± 117.9 μM, controls: 602.2 ± 295.6) and at the end of exercise (CF: 430.9 ± 180.6, controls: 1147.5 ± 473.5). There were no differences in the rates of CHO oxidation, insulin or glucose between groups.
  
  
  CONCLUSIONS
  Fat metabolism during exercise is impaired in boys with CF and may be attributed to an inability to mobilize FFA.
authors.affiliation: Child Health & Exercise Medicine Program, Department of Pediatrics, McMaster University, Hamilton, ON, Canada.
authors.forename: Thanh
authors.initials: T
authors.lastname: Nguyen
authors.affiliation: Child Health & Exercise Medicine Program, Department of Pediatrics, McMaster University, Hamilton, ON, Canada.
authors.forename: Joyce
authors.initials: J
authors.lastname: Obeid
authors.affiliation: Exercise Metabolism Research Group, Department of Kinesiology, McMaster University, Hamilton, ON, Canada; Department of Kinesiology, McMaster University, Hamilton, ON, Canada.
authors.forename: Jeff M
authors.initials: JM
authors.lastname: Baker
authors.affiliation: Child Health & Exercise Medicine Program, Department of Pediatrics, McMaster University, Hamilton, ON, Canada; Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Tim
authors.initials: T
authors.lastname: Takken
authors.affiliation: Cystic Fibrosis Clinic, McMaster Children's Hospital, Hamilton, ON, Canada.
authors.forename: Linda
authors.initials: L
authors.lastname: Pedder
authors.affiliation: Exercise Metabolism Research Group, Department of Kinesiology, McMaster University, Hamilton, ON, Canada; Department of Kinesiology, McMaster University, Hamilton, ON, Canada.
authors.forename: Gianni
authors.initials: G
authors.lastname: Parise
authors.affiliation: Child Health & Exercise Medicine Program, Department of Pediatrics, McMaster University, Hamilton, ON, Canada. Electronic address: timmonbw@mcmaster.ca.
authors.forename: Brian W
authors.initials: BW
authors.lastname: Timmons
mesh_terms: D000293:Adolescent; D001642:Bicycling; D001786:Blood Glucose / Q000378:metabolism; D002648:Child; D003550:Cystic Fibrosis / Q000378:metabolism* / Q000503:physiopathology*; D004040:Dietary Carbohydrates / Q000378:metabolism; D004041:Dietary Fats / Q000378:metabolism*; D004734:Energy Metabolism / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005230:Fatty Acids, Nonesterified / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000097:blood; D019369:Life; D050356:Lipid Metabolism / Q000502:physiology; D008297:Male; D008954:Models, Biological; D009752:Nutritional Status; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000502:physiology
chemical_list: D001786:Blood Glucose; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D005230:Fatty Acids, Nonesterified; D007328:Insulin
keywords: Cycling; Cystic fibrosis; Free fatty acids; Substrate utilization